The tablet can take over from the desktop ( which these days is most likely a laptop that can be connect to monitor and keyboard) when it has all the apps that the desktop has but most importantly a keyboard. I have used on screen keyboards for a long time and they are fine for a quick response to email,etc but not writing a proposal or a design document. So when tablets have all the apps+monitor(tablet screens are ok)+keyboard the they can , oh but wait isn't that what a laptop is .